This invention relates to a soil degree determining apparatus for determining wrinkles, folds, etc. of a printed area of printed matter.
Many conventional apparatuses for determining soil degree of printed matter employ a method for measuring the density of a printed area or a non-printed area of printed matter to thereby detect the soil degree of the printed matter. Japanese Patent Application KOKAI Publication No. 60-146388, for example, discloses a method for dividing printed matter into a printed area and a non-printed area, setting, as reference data, an integration value of light reflected from the printed matter or light transmitted through the printed matter, and determining whether or not a soil exists on the matter. In this method, a soil such as discoloration, a spot, blurring, etc., detected as a block change in the density of a local area, is measured as a change in the integration value (i.e. sum) of the densities of pixels corresponding to the non-printed area or the printed area.
Further, there is a method for accurately determining a fold, a wrinkle, etc. of printed matter as a linear area changed in density, instead of determining dirt as a block change in the density of local area of printed matter. Japanese Patent Application KOKAI Publication No. 6-27035, for example, discloses a method for measuring a fold and wrinkle of a non-printed area.
As described above, in the prior art, the soil degree of printed matter is determined by measuring integration values of densities of pixels corresponding to the printed and non-printed areas of the printed matter, or measuring a fold and wrinkle of the non-printed area of the printed matter. However, a method for determining the soil degree of printed matter by measuring a fold and wrinkle of the xe2x80x9cprinted areaxe2x80x9d of the matter is not employed in the prior art for the following reason.
In general, the density of a soil detected as a linear area changed in density (in the case of a fold, wrinkle, etc.) is quite different from the density of a sheet of plain paper. The conventional method for measuring a fold and wrinkle in a xe2x80x9cnon-printed areaxe2x80x9d uses this density difference. Specifically, differentiation processing is performed to emphasize the change in density caused at a fold or a wrinkle, thereby extracting pixels corresponding to the fold or the wrinkle by binary processing, and calculating the number of the pixels or the average density of the pixels. Thus, the soil degree is measured.
On the other hand, concerning the xe2x80x9cprinted areaxe2x80x9d, there is a case where a pattern having lines of different widths and/or including pattern components of different densities of colors is printed in the printed area, or where the entire xe2x80x9cprinted areaxe2x80x9d is coated with printed ink as in photo-offset printing. In an image obtained in the prior art by detecting light reflected from or transmitted through printed matter, a fold or a wrinkle existing in its printed area cannot be discriminated therefrom, which means that a soil cannot be extracted from the printed area. This is because the density of a soil such as a fold or a wrinkle is similar to that of the printed area. Accordingly, it is very difficult in the prior art to extract and measure a fold and/or a wrinkle in the printed area.
For example, imagine a case where the integration value of densities of pixels corresponding to ink and a soil on the entire printed area that includes a fold and/or a wrinkle is measured to detect the soil degree of the printed area. In this case, it is difficult to discriminate the density of ink from the density of a soil of the fold or the wrinkle, and the number of pixels corresponding to the fold or the wrinkle is smaller than that of the entire printed area. Moreover, variations exist in the density of ink of the printed image. For these reasons, a change in density due to the fold or the wrinkle cannot be determined from the integration value of pixel densities of the printed area.
As described above, the conventional methods cannot measure a fold and/or a wrinkle in a printed area of the printed matter.
In addition, even if a soil on a printed area or a non-printed area of printed matter due to a fold or a wrinkle can be measured, it is still difficult in the prior art to discriminate a fold or a wrinkle from a tear that will easily occur in an edge portion of the printed matter. This is because in the case of a tear differing from the case of a hole or a cutout space, it has a linear area changed in density as in a fold or a wrinkle, if two tear areas are aligned with each other and an image of the aligned areas is input.
It is an object of the invention to provide a soil degree determining apparatus that can determine, as humans do, a fold of a printed area of printed matter, unlike the conventional apparatuses.
It is another object of the invention to provide a soil degree determining apparatus capable of discriminating between a fold and a tear of printed matter, which cannot be distinguished in the prior art.
The present invention uses a phenomenon, appearing when an image of to-be-inspected printed matter is input using light of a near-infrared wavelength, in which the reflectance or the transmittance of a fold or a wrinkle of the printed matter is much lower than that of a printed area or a non-printed area of the printed matter.
According to one aspect of the invention, there is provide a soil degree determining apparatus for determining soil degree of printed matter, comprising:
image input means for inputting an IR image of printed matter to be subjected to soil degree determination, using IR light having a near-infrared wavelength; image extracting means for extracting image data in a particular area including a printed area, from the IR image input by the image input means; changed-section extracting means for extracting, on the basis of the image data in the particular area extracted by the image extracting means, a non-reversible changed section caused when the printed matter is folded, thereby providing data concerning the changed section; feature quantity extracting means for extracting a feature quantity indicative of a degree of non-reversible change in the particular area, on the basis of the data concerning the changed section and provided by the changed-section extracting means; and determining means for estimating the feature quantity extracted by the feature quantity extracting means, thereby determining a soil degree of the printed matter. The image input means has an IR filter for filtering wavelength components other than the near-infrared wavelength.
The input of an image of printed matter using light of a near-infrared wavelength enables determination of a fold of a printed area of printed matter as humans do, unlike the conventional apparatuses.
Furthermore, the present invention can detect, by performing image input using light obliquely transmitted through printed matter, a gap formed when a tear occurs at an edge portion of the printed matter and two portions resulting from the tear displace from each other, thereby enabling distinguishing of a tear from a fold or a wrinkle, which cannot be realized in the prior art. Thus, the present invention can obtain a soil degree determination result similar to that obtained by humans.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.